Maintenance of hyperalgesia requires changes in the expression of proteins that lead to an increase in synaptic strength. Data generated in this proposal will test the hypothesis that peptides released in the spinal cord in response to tissue damaging stimuli activate receptors on spinal neurons that increase gene expression, resulting in increased expression of proteins that underlie hyperalgesia. Data will be generated to address the following questions: 1) Does SP activate NFAT-dependent gene transcription in spinal neurons? 2) Does SP facilitate effects of CGRP on CREB-dependent gene transcription in spinal neurons? 3) Do SP and CGRP increase expression of proteins relevant to hyperalgesia in spinal neurons in vitro? 4) Do SP and CGRP increase expression of these proteins in spinal neurons in vivo? 5) Does treatment with SP or CGRP increase secondary hyperalgesia? 6) Do endogenous SP and CGRP contribute to the maintenance of secondary hyperalgesia during peripheral inflammation? Immunoblot analysis and real time PCR will be used to quantify the effects of SP and CGRP on the expression of four proteins that are known to be increased in the spinal cord during peripheral inflammation and that contribute to hyperalgesia: neurokinin-1 receptor, cyclo-oxygenase 2, type 1 nitric oxide synthase and inositol triphosphate receptor. Behavioral assays of nociception will be used to test whether treatment with SP and CGRP is sufficient to increase hyperalgesia, antagonists of SP and CGRP receptors will be used to determine whether endogenous SP and CGRP are necessary to support the increase in nociceptive responses that occurs in a model of peripheral inflammation. The experiments will generate new information concerning the effects of SP and CGRP on protein expression in spinal neurons in general as well as 4 proteins that contribute to hyperalgesia. If the hypothesis is proven to be true, the data will provide evidence for a new therapeutic strategy that may be effective in treating peripheral inflammatory diseases.